Livestock stress has long been recognised as having a major impact on the post-mortem quality of the animal tissue.1,2,3,4,5 
It is well known that stress causes the depletion of an animal's energy reserves through depletion of glycogen in muscle tissue, and causes an increase in pH. pH values in excess of 5.8 result in poor meat quality. PH values in the range 5.8-6.1 cause toughness and furthermore, values in the range 5.8-7.00 cause increasing deterioration A, B, C. Qualities affected include:
Colour: the higher the ultimate pH the darker the meat colour. Customer demand is for bright red, rather than dark, meats;
Keeping ability: which decreases with the increase in pH;
Texture: high pHs tend to produce rubbery, watery meats; and
Tenderness: both high and low pH meats may be tender.
However, because of the other disadvantages associated with high pH, low pH tender meat is preferable. High pH, poor quality meats are not suitable for the export market and are often down-graded resulting in multi-million dollar losses to the primary meat sector each year.
Major causes of stress include rounding up and lairage of animals on the farm, crowded transport conditions, driving animals over long distances without rest, and handling procedures at processing plants, such as prodding and washing. It has also been recognised that by feeding an animal prior to slaughter, muscle energy reserves can be restored and down-grading avoided.4 In ruminant animal such replenishment can take more than a day. In a monogastric, this is normally quicker. If a technology existed that could recognise at risk animals prior to processing then these animals could be treated.
U.S. Pat. No. 5,458,418, and U.S. Pat. No. 5,595,444 disclose methods of detecting poor meat quality in animals using infrared thermography. A single thermographic temperature measure is taken of an animal prior to slaughter. Animals with a thermograph outside a a predetermined test temperature range are rejected as likely to have meat of poor quality. Similarly, for a group of animals, animals showing a significant deviation in mean image temperature compared to the group mean temperature are rejected as likely to have meat of poor quality.
The infrared thermography methods disclosed in these patents are subject to a number of drawbacks. A one point temperature measurement prior to slaughter cannot reflect thermal history, nor accurately predict its effect on meat quality. The single reading may detect acute stress shortly prior to slaughter but not cumulative stress over a period of time. A further drawback is that an animal may be rejected for slaughter as a consequence of its mean image temperature in comparison with the group and not by reference to an absolute standard. Thus, animals may be unnecessarily downgraded. It is for this reason that infrared thermography has not performed well in practice as a predictor of meat quality.
It is an object of the present invention to provide a method for identifying stressed animals, or at least to provide the public with a useful choice.
The present applicant has found that in all animals subjected to stress, body temperature changes produce either an increase or decrease in skin heat loss. Changes in body temperature both up and down from the homeostatic norm are energetic that is energy must be used to re-establish norm by pulling body temperature up or lowering it (heat production or heat loss). Often these adjustments are quick and not reflected in deep body temperatures. They are, however, reflected in skin and surface temperatures and peripheral blood flow mechanisms ie. in the outer body. High energy expenditure can be made with little change seen in core temperatures. Falls in body/skin temperature are as (if not more) energetically demanding than rises.
In terms of stress measurement both a fall, or rise, in skin/body temperature can be an important indicator of stress, and such changes can be important both acutely and chronically (i.e. a number of changes) over time. In terms of predicting meat quality, cumulative stress, or more specifically cumulative energy expenditure, is more important than acute stress (other than extreme acute stress). A cumulative measure of skin/body temperature changes (both up and down) can provide an index over time of the amount of energy spent by the animal. The more energy spent by the animal over a 24 hour period prior to its slaughter the more likely that the meat will be of poor quality if the animal is not allowed an additional period to replenish its energy stores via eating.
As stress has energetic consequences it can influence production return and can have implications for animal welfare. A simple tool for measuring and offering quality control on these would be useful.
Animals that have meat ultimate pH levels in an acceptable range (pH 5.5-5.8) show a weak correlation between body temperature at slaughter and the actual meat pH. This correlation is greater if changes in body temperature are integrated over time, preferably for at least 12 hours prior to slaughter. A convenient way to do this is to use a cumulative variance around an averaged body temperature for an individual animal. Higher cumulative variances in temperature predict higher pH meat, a measure that relates to the amount of glycogen residing in the meat. Based on the applicant's findings of the correlation between pH, temperature and stress, it is proposed that animal sensor devices may be produced to monitor body temperature, and its variance, as a measure of an animal's stress level and as a predictor of meat quality.
Animal temperature sensors are known in the art. For example, in U.S. Pat. No. 3,781,837 and U.S. Pat. No. 4,865,044, tympanic temperature sensors are employed. In U.S. Pat. No. 4,854,328, a temperature sensor device is implanted at the base of an animal's skull. An ear tag component is provided which incorporates a unit for receiving signals from the implanted sensor, and indicating means responsive to the generated signal. In the case of U.S. Pat. No. 4,865,044, an ear tag is employed to contain the bulk of the temperature sensor circuitry, at a position remote from the tympanic animal temperature sensor.
The use of tympanic and surgically implanted sensor devices is usually contraindicated because of the high invasive load on the animal. Further, dislodgement problems are also encountered with tympanic sensors. Where implanted devices are used, incisions can easily become infected and the implantation procedure is more difficult to carry out.
Accordingly, it is a further object of at least a preferred embodiment of this invention to provide a temperature sensing device which overcomes some of these disadvantages, or again at least provides the public with a useful choice.
In a first aspect, the present invention may be broadly said to consist in a method of providing an indication of pH levels in an animal, the method comprising:    a) obtaining measurements corresponding to the body temperature of the animal at periodic time intervals;    b) applying an algorithm to the measurements obtained from a) which algorithm cumulatively takes account of variations in body temperature over time; and    c) comparing the results of the algorithm to a predetermined threshold or correlating the results of the algorithm with a pH standard.
One simple algorithm is to calculate cumulative temperature variance which may be calculated in a number of ways. A simple method discussed in greater detail below comprises:    a) measuring the animal's body temperature at intervals over a period of time;    b) determining that animal's average body temperature reading over that period of time;    c) calculating the variance between each temperature measurements taken under a) and the average determined in step b); and    d) adding all variance values calculated according to step c) to obtain the cumulative temperature variance score.
To calculate cumulative temperature variance at least two temperature readings must be taken. For accuracy, it is preferred that multiple readings of 10 or more are taken in a predetermined time period.
From our discussions above, the reader will appreciate that the pH level predicted is an indicator of meat quality, with a pH level greater than 5.8 indicating meat of poor quality.
In a further aspect, the present invention provides a method of providing an indication of stress levels in an animal, the method comprising:    a) obtaining measurements corresponding to the body temperature of the animal at periodic time intervals;    b) applying an algorithm to the measurements obtained from a) which algorithm cumulatively takes account of variations in body temperature over time; and    c) comparing the results of the algorithm to a predetermined threshold or correlating the results of the algorithm with a stress standard.
In another aspect, the present invention provides a method of measuring stress levels in an animal, the method comprising measuring the animal's pH level using a method of the invention, a pH level greater than 5.8 to 6.2 indicating a stressed animal.
In accordance with a further aspect of the present invention there is provided a method of providing an indication of meat quality in an animal, the method comprising:    a) obtaining measurements corresponding to the body temperature of the animal at periodic time intervals;    b) applying an algorithm to the measurements obtained from step a), which algorithm cumulatively takes account of variations in body temperature over time; and    c) comparing the results of the algorithm to a predetermined threshold or correlating the results of the algorithm with a meat tenderness standard.
By way of example, the New Zealand lamb AC & A standard may be used as a meat tenderness standard. Outputs from the algorithm may be pre-calibrated to the standard so that in use, the result from the algorithm may be compared with the standard to give an indication of meat tenderness.
In a specific form of the invention, the algorithm may calculate a mean of the measurements obtained in step (a); calculate a variance of each measurement from the calculated mean; and integrate the variances over time. In one preferred form of this embodiment, the measurements may be taken for a predetermined time period and a final mean calculated at the end of that predetermined time period. The integration of the variances will then be conducted over the predetermined time period. In an alternative version of this simple algorithm based on variances from a mean temperature, a running mean may be progressively determined from the measurements obtained in step (a). At each stage, the variation of the temperature measurement from the previous calculated running mean may be integrated over time. This reduces the memory requirements of the device to implement the method.
More sophisticated algorithms may be employed which depart from the simple method of calculating the variances from the mean. These more sophisticated algorithms may determine a cumulative value which is dependent on progressive changes or trends in the measurements obtained from step (a), rather than being dependent on absolute temperature measurements. This avoids the need to calibrate the temperature sensors.
Thus the measurements obtained from step (a) may or may not be actual temperature measurements. For example, in any embodiment utilising absolute temperature values, relatively inexpensive thermistors may be employed to obtain the temperature measurements with the circuitry in which the thermistors are employed compensating for any variation in the measured temperature from the real temperature. This calibration may be effected by calculating a correction coefficient and programming this into a microprocessor employed in the circuit.
In more sophisticated algorithms which rely on temperature changes rather than absolute values, no calibration may be required.
The body temperature is preferably measured on the outer part of the animal since temperature adjustments to accommodate stress appear to be more pronounced on the outer part of the animal compound to core temperatures. In a most preferred form of the invention, the skin measurements may be taken e.g. on the ear of the animal.
In any embodiment in which the outer body temperature is determined on the skin, a correction for the effects of ambient temperature will be required. This can be achieved through the use of an ambient temperature sensor. Additionally, correction for solar radiation may also be required where the skin temperature sensor is exposed to sunlight. The body temperature may also be measured in more internal locations such as the inner ear. This may avoid the requirement for ambient temperature compensation. However stress induced temperature fluctuation may be less and more sensitive temperature measuring devices may be required when measuring in this position.
In the simplest of embodiments where the algorithm is applied at the end of the predetermined time period, a device implementing the method may be provided with an indicator to indicate the results of the comparison step conducted in step (c). If the failure of step (c) is indicated by way of a flashing light or audible alarm then the same facility may be used to periodically indicate the correct functioning of the device. For example, where a frequently flashing light indicates failure of step (c), an intermittent flashing of the same light may merely indicate that the device is functioning. A non flashing light will thus indicate to an attendant that the device has malfunctioned or has lost power.
In the embodiment where the algorithm is progressively employed to the measurements obtained in step (a), step (c) may be employed after each implementation of the algorithm. Thus, if the animal fails the test at any point throughout a predetermined time period then an indicator may be employed to show that the animal has failed the test. The method may then be reemployed starting at the beginning of the predetermined time period. If at any time during the retest the animal fails step (c) again then the same indicator will indicate failure of the test and the process will be repeated. However, should the animal progress to the end of the predetermined time period without failing step (c) then an alternative indication may be given that the animal has passed the test for the full duration of the predetermined time period and thus is fit for slaughter. Suitably once the animal has reached this point it should be slaughtered without further delay and without the opportunity for the animal to incur further stress.
In one specific implementation of the method, it may not be necessary to wait for the full duration of a specific predetermined time period if the time period from rounding up to delivery of the animals to the abattoir is less than the predetermined time period. In the method which progressively applies the algorithm, if the animal has not yet failed the test during the time thus far and if the conditions before the testing started were such that the animals were unlikely to be subjected to stress, then the animals might proceed to immediate slaughter.
In accordance with another aspect of the present invention, there is provided a system for providing an indication of meat quality in an animal to be slaughtered, the system including:                a body mountable measurement device for obtaining measurements corresponding to the body temperature of the animal at periodic time intervals over a period of 3-36 hours;        a processor having an input means to receive the measurements from the measurement device, the processor operable to implement an algorithm to the measurements, which algorithm cumulatively takes account of variations in body temperature over time, wherein the processor has an output means for the result of the algorithm.        
The system may be implemented in an all-in-one indicator device. Such a device may be mounted on the animal eg ear tag, tail tag or provided on a collar. The tag may also incorporate the measurement device. In an alternative form of the invention, the measurement device may be remote from the tag. The measurements may be sent to the processor by way of a transmitter or by a cable. In one preferred form of the invention, the measurement device may be provided by way of a thermistor to be deposited in the inner ear canal of the animal with a cable connected to an ear tag which houses the processor.
In yet another embodiment of the present invention, the processor may be provided by way of a remote computer. In this embodiment, a device for mounting on the animal will suitably incorporate transmitters to send the measurements to the remote computer. The remote computer may be a field device which is able to sense and account for ambient temperatures and solar radiation. Alternatively, a separate field device may be provided to send information relating to ambient temperature and solar radiation to a remote processor. The remote computer also receives the measurements from the measurement device provided on the animal either directly or via the field device.
The output from the processor may be in any of various forms. A simple numeric value may be output for the attendant to decide whether or not it falls within acceptable limits. The value might be compared to a meat tenderness scale for quantitve assessment as to whether it falls within acceptable limits. However, in most embodiments it is preferred that the processor is operable to compare the outputs of the algorithm to a predetermined threshold. The system may also include an indicator to indicate where the output of the algorithm has exceeded the predetermined threshold. Any of the features described in connection with the above-described method of indicating meat quality may be implemented in the system.
In accordance with yet another aspect of the present invention, there is provided a system for indicating cumulative stress in an animal, the system including:                a body mountable measurement device for obtaining measurements corresponding to outer body temperature of the animal at periodic time intervals over a period of 3-36 hours:        a processor having an input to receive measurements from the measurement device, the processor operable to implement an algorithm to the measurements, which algorithm cumulatively takes account of variations in body temperature over time, wherein the processor has an output for the result of the algorithm.        
The system for providing an indication of stress may be implemented in any of the various forms discussed above for the system providing an indication of meat quality. Such a system for indicating cumulative stress might have particular application to animals where the effects of stress might be dangerous either to the animal itself, to other animals or in particular to humans. For example, horses might be more prone to erratic behaviour and a danger to their riders if they are subjected to sustained periods of stress. A system implemented in the form of an all-in-one indicator device may provide simple indication to the rider that the animal is stressed and needing rest or food.
Preferably, the processor is also operable to compare the output of the processor with a predetermined threshold. The system preferably incorporates an indicator to provide indication that the predetermined threshold has been exceeded. In an all-in-one indicator device, this may be implemented by a simple visual indicator such as a flashing led. In an embodiment with a remote computer then the output of the computer may provide the identification numbers of those animals which have exceeded the threshold.
In accordance with a still further aspect of the invention, there is provided a system of providing an indication of ultimate meat pH of an animal, the system including:                a body mountable measurement device for obtaining measurements corresponding to outer body temperature of the animal at periodic time intervals over a period of 3-36 hours:        a processor having an input to receive measurements from the measurement device, the processor operable to implement an algorithm to the measurements, which algorithm cumulatively takes account of variations in body temperature over time, wherein the processor has an output for the result of the algorithm.        
In a further aspect, the present invention provides:
A temperature sensing device including:                a tag having an attachment portion to extend through a body part of an animal, the tag incorporating an indicator means; and        one or more animal temperature sensors disposed on/in the attachment portion for contact with the animal during use.        
Preferably, the tag is an ear tag. Preferably, an ambient temperature sensor is also provided 100 on the tag. Further, the tag may be provided with comparison means to compare the ambient temperature with the animal temperature. An indicator may also be disposed on the tag, the indicator being responsive to the comparison means.
Desirably, the tag comprises a one piece moulded body.
Also contemplated by the present invention is the use of the temperature sensing device in the methods of the invention as described above.
This invention may also be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, and any or all combinations of any two or more of said parts, elements or features, and where specific integers are mentioned herein which have known equivalents in the art to which this invention relates, such known equivalents are deemed to be incorporated herein as if individually set forth.
The invention consists in the foregoing and also envisages constructions of which the following give examples.